Shoe-forming member and shoe

ABSTRACT

Provided is a shoe-forming member that has excellent adhesion. The shoe-forming member is formed using a thermoplastic elastomer containing an aromatic polymer having a poly-α-methylstyrene structure in a matrix together with a polypropylene resin.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 16/582,168 filed Sep. 25, 2019, which is acontinuation of U.S. patent application Ser. No. 15/506,360 filed Feb.24, 2017, which is a 371 of international PCT/JP2015/074458, filed Aug.28, 2015 which is a continuation of international PCT/JP2014/072724,filed Aug. 29, 2014, which are hereby incorporated herein by referencesin its entirety.

FIELD

The present invention relates to a shoe-forming member and a shoe, morespecifically, to a shoe-forming member containing a thermoplasticelastomer and a shoe including such a shoe-forming member.

BACKGROUND

Conventionally, upper materials and sole materials of sports shoes orthe like are mostly formed using crosslinked rubber. Forming theshoe-forming members such as upper materials and sole materials usingthermoplastic elastomers has been studied in view of recyclability andformability (see Patent Literature 1 below).

CITATION LIST Patent Literature

Patent Literature 1: JP 2006-192723 A

SUMMARY Technical Problem

Urethane thermoplastic elastomers and olefin thermoplastic elastomersare known as such thermoplastic elastomers. Olefin thermoplasticelastomers in which domains composed of crosslinked elastomers aredispersed in a matrix of a polypropylene resin have excellent hydrolysisresistance as compared with urethane thermoplastic elastomers. Further,the aforementioned olefin thermoplastic elastomers are suitable asmaterials of shoe-forming members since they have a comparatively lowdensity and less chances of embrittlement at low temperature. On theother hand, the olefin thermoplastic elastomers are less likely to exerthigh adhesiveness with common adhesives. Therefore, even when membersmade of olefin thermoplastic elastomers are used for forming a shoe, theportions in which they can be used may possibly be limited.

The present invention aims to solve such a problem, and an objectthereof is to improve the adhesiveness of a shoe-forming membercontaining an olefin thermoplastic elastomer.

Solution to Problem

In order to solve the aforementioned problem, a shoe-forming memberaccording to the present invention contains a thermoplastic elastomer,the thermoplastic elastomer containing: a matrix including apolypropylene resin and an aromatic polymer; and a domain containing acrosslinked elastomer, wherein the aromatic polymer has apoly-α-methylstyrene structure in at least part of its molecule.

Further, in order to solve the aforementioned problem, a shoe accordingto the present invention includes the aforementioned shoe-formingmember.

Advantageous Effects of Invention

The thermoplastic elastomer contained in the shoe-forming member of thepresent invention contains an aromatic polymer having apoly-α-methylstyrene structure together with a polypropylene resin in amatrix in at least part of its molecule. The shoe-forming member canexert excellent adhesiveness by containing the specific aromatic polymertogether with the polypropylene resin in the matrix of the thermoplasticelastomer.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic view showing an aspect of a shoe using ashoe-forming member according to an embodiment.

FIG. 2 is an image showing a microstructure of a thermoplastic elastomerused for forming a shoe sole member (observation results using an atomicforce microscope).

DESCRIPTION OF EMBODIMENTS

Hereinafter, a shoe-forming member of the present invention will bedescribed by way of the embodiments. FIG. 1 shows a shoe including ashoe-forming member of this embodiment. A shoe 1 has an upper material 2and shoe sole members 3 and 4. The shoe 1 has a midsole 3 and an outersole 4 as the shoe sole members. The upper material 2 of the shoe 1 hasa layer structure including at least one piece of reinforcing sheetmaterial 21. Specifically, the shoe-forming member of this embodiment ispreferably the reinforcing sheet material 21, the outer sole 4, or thelike.

First, a thermoplastic elastomer that is suitable for forming thereinforcing sheet material 21 and the outer sole 4 will be described.The thermoplastic elastomer is a polyolefin thermoplastic elastomer,more specifically, a polypropylene thermoplastic elastomer. Thethermoplastic elastomer has a microphase-separated structure formed by amatrix containing a polypropylene resin and an aromatic polymer, and adomain composed of a crosslinked elastomer.

The polypropylene resin may be any one of a homopolypropylene resin thatis a propylene homopolymer, a random polypropylene resin that is arandom copolymer of propylene and ethylene, and a block polypropyleneresin that is a block copolymer of propylene and ethylene.

The aromatic polymer constituting the matrix together with thepolypropylene resin may be a homopolymer resin (homopolymer) ofα-methylstyrene monomer, or a copolymer resin (copolymer) composed oftwo or more types of monomers, as long as it has a poly-α-methylstyrenestructure in at least part of its molecule.

In the case where the aromatic polymer is a homopolymer, specificexamples of the α-methylstyrene monomer as a constituent unit thereofinclude α-methylstyrene, α-methyl-o-methylstyrene,α-methyl-m-methylstyrene, α-methyl-p-methylstyrene,α-methyl-2,6-dimethylstyrene, α-methyl-2,4-dimethylstyrene, andα-methyl-2,4,6-trimethylstyrene. That is, specific examples of thehomopolymer include poly-α-methylstyrene resin,poly-α-methyl-o-methylstyrene resin, poly-α-methyl-m-methylstyreneresin, poly-α-methyl-p-methylstyrene resin,poly-α-methyl-2,6-dimethylstyrene resin,poly-α-methyl-2,4-dimethylstyrene resin, andpoly-α-methyl-2,4,6-trimethylstyrene resin.

In the case where the aromatic polymer is a copolymer resin, specificexamples thereof include a copolymer resin of two or more types of theα-methylstyrene monomer. Further, in the case where the aromatic polymeris a copolymer resin, specific examples thereof include a copolymerresin of a vinyl monomer that is copolymerizable with theα-methylstyrene monomer and one or more types of the α-methylstyrenemonomer. In the case of such a copolymer resin, the aromatic polymer maybe a block copolymer resin or a graft copolymer resin.

Examples of the vinyl monomer that is copolymerizable with theα-methylstyrene monomer include olefin monomers, acrylic monomers,styrene monomers, vinyl ether monomers, and diene monomers.

Specific examples of the olefin monomers include ethylene, propylene,1-butene, 2-methyl-1-butene, 3-methyl-1-butene, pentene, hexene,cyclohexene, 4-methyl-1-pentene, vinyl cyclohexane, octene, andnorbornene.

Specific examples of the acrylic monomers include (meth)acrylic acid,methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate,isopropyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate,hexyl (meth)acrylate, octyl (meth)acrylate, ethylhexyl (meth)acrylate,dodecyl (meth)acrylate, myristyl (meth)acrylate, palmityl(meth)acrylate, stearyl (meth)acrylate, behenyl (meth)acrylate,cyclohexyl (meth)acrylate, and phenyl (meth)acrylate.

Specific examples of the styrene monomers include styrene,4-methylstyrene, 4-ethyl styrene, 4-propyl styrene, 4-t-butyl styrene,4-cyclohexyl styrene, 4-dodecyl styrene, 2-ethyl-4-benzyl styrene,4-(phenyl butyl) styrene, 2,4,6-trimethylstyrene, monochlorostyrene,dichloro styrene, monobromostyrene, dibromostyrene, and methoxystyrene.

Specific examples of the vinyl ether monomers include methyl vinylether, ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether,n-butyl vinyl ether, sec-butyl vinyl ether, tert-butyl vinyl ether,isobutyl vinyl ether, methyl propenyl ether, and ethyl propenyl ether.

Specific examples of the diene monomers include butadiene, isoprene,hexadiene, cyclopentadiene, cyclohexadiene, dicyclopentadiene, divinylbenzene, and ethylidene norbornene.

These vinyl monomers may have a functional group such as a hydroxylgroup and an amino group.

The aromatic polymer constituting the matrix together with thepolypropylene resin in this embodiment is preferably such a homopolymeras mentioned above, preferably poly-α-methylstyrene resin.

The ratio of the polypropylene resin and the aromatic polymer in thethermoplastic elastomer is not specifically limited, but it ispreferable that the aromatic polymer be contained in the thermoplasticelastomer at a mass ratio equal to or higher than the ratio of thepolypropylene resin, for allowing the reinforcing sheet material 21 andthe outer sole 4 to exert excellent adhesiveness and excellent abrasionresistance. Specifically, the aromatic polymer is preferably containedin the thermoplastic elastomer at a mass ratio of 1.5 times or more ofthe polypropylene resin, more preferably 7.5 times or more thereof.Further, the aromatic polymer is preferably contained in thethermoplastic elastomer at a mass ratio of 20 times or less of thepolypropylene resin.

The crosslinked elastomer constituting the domain in the thermoplasticelastomer is not specifically limited, but styrene elastomers arepreferable in view of the affinity or the like with the matrix. That is,the crosslinked elastomer constituting the domain is preferably acrosslinked elastomer obtained by crosslinking a styrene polymer such asstyrene-ethylene-butylene copolymer resin (SEB),styrene-butadiene-styrene copolymer resin (SBS), a hydrogenated productof SBS (styrene-ethylene-butylene-styrene copolymer resin (SEBS)),styrene-isoprene-styrene copolymer resin (SIS), a hydrogenated productof SIS (styrene-ethylene-propylene-styrene copolymer resin (SEPS)),styrene-isobutylene-styrene copolymer resin (SIBS),styrene-butadiene-isoprene-styrene copolymer resin (SBIS), ahydrogenated product of SBIS(styrene-ethylene-ethylene/propylene-styrene copolymer resin (SEEPS)),styrene-butadiene-styrene-butadiene copolymer resin (SBSB), andstyrene-butadiene-styrene-butadiene-styrene copolymer resin (SBSBS),using a crosslinking agent. Among these, the domain is preferably acrosslinked elastomer obtained by crosslinking SEBS or SEEPS,particularly preferably a crosslinked elastomer obtained by crosslinkingSEEPS, for allowing the thermoplastic elastomer to exert excellentabrasion resistance.

In view of the dispersibility of the domain in the matrix, it ispreferable that the domain be formed by supplying such a styrene polymeras mentioned above to a kneading machine such as an extruder togetherwith the polypropylene resin and the aromatic polymer, to allow thestyrene polymer to be dynamically crosslinked in the kneading machine.

When producing a thermoplastic elastomer by performing the dynamiccrosslinking in a kneading machine, it is not necessary to supply thestyrene polymer, the polypropylene resin, and the aromatic polymer tothe kneading machine all at once, and after a primary kneaded mixture isobtained by first kneading of the styrene polymer, the polypropyleneresin, and a part of the aromatic polymer using the kneading machine,second kneading may be performed by adding the rest to the primarykneaded mixture. As a method for producing the thermoplastic elastomer,it is preferable to employ a method of adding the polypropylene resinand a part or all of the aromatic polymer afterwards to the kneadingmachine, in which after a primary kneaded mixture having a highercontent of the styrene polymer than the thermoplastic elastomer to beproduced is produced in the presence of the crosslinking agent, andthereafter a part or all of the constituents of the matrix are added tothe primary kneaded mixture for second kneading. According to such apreferable embodiment, the styrene polymer and the crosslinking agentcan be allowed to exist in the primary kneaded mixture at highconcentration, and thus the crosslinking efficiency of the styrenepolymer can be improved.

The aromatic polymer in this embodiment is incompatible with thepolypropylene resin. The incompatibility between the aromatic polymerand the polypropylene resin can be confirmed, for example, by producinga melt kneaded product containing them at a mass ratio of 1:1 andchecking the presence of a phase separation structure in the meltkneaded product.

The thermoplastic elastomer of this embodiment has a specificmorphology. Specifically, such domains of the thermoplastic elastomer inthis embodiment are dispersed in the matrix while being covered by thepolypropylene resin. Here, the phrase “domains being covered by thepolypropylene resin” does not have a restrictive meaning such that “allthe domains are covered by the polypropylene resin”. That is, the phrase“domains being covered by the polypropylene resin” has a meaning thatincludes the case where “some of the domains are covered by thepolypropylene resin”. Further, the phrase “domains being covered by thepolypropylene resin” does not have a restrictive meaning such that “thepolypropylene resin covers the entire surfaces of the domains”. That is,the phrase “domains being covered by the polypropylene resin” has ameaning that includes the case where “the polypropylene resin partiallycovers the surfaces of the domains”

The polypropylene resin of this embodiment has a low melt viscosity ascompared with the aromatic polymer and thus is effective for achievingexcellent formability of the thermoplastic elastomer. That is, in thethermoplastic elastomer when it is heated, the polypropylene resin thathas melted and thus has low viscosity is present around the domains, andtherefore the polypropylene resin exhibits a function as a lubricant inplastic deformation. The melt viscosity of the polypropylene resin andthe aromatic polymer can be measured using a twin bore capillaryrheometer (barrel diameter: 15 mm) having a die (die diameter: 1 mm, dielength: 16 mm) attached to one end and an orifice having a diameter of 1mm on the other end, for example, under conditions of a temperature of230° C. and a shear speed of 50 (1/s).

For exhibiting the aforementioned function more significantly, it ispreferable that some of the domains be entirely covered by thepolypropylene resin. Whether the thermoplastic elastomer has such amorphology can be confirmed, for example, using an atomic forcemicroscope. This will be explained with reference to FIG. 2 . FIG. 2shows the observation results of the thermoplastic elastomer accordingto this embodiment using an atomic force microscope, in which whiteportions are the polypropylene resin, and black portions surrounded bythe polypropylene resin are the crosslinked styrene elastomer. Further,the other portions in FIG. 2 are mainly portions occupied by thearomatic polymer. Such dispersion of the domains of the thermoplasticelastomer in the matrix while being covered by the polypropylene resincan be confirmed using an atomic force microscope.

The content of the crosslinked styrene elastomer serving as the domainsin the thermoplastic elastomer is preferably 15 mass % or more and 50mass % or less, for allowing the reinforcing sheet material 21 and theouter sole 4 to exert excellent flexibility and excellent strength.

Specific examples of the crosslinking agent used for crosslinking thestyrene polymer to give a crosslinked elastomer include organicperoxides. Specific examples of the organic peroxides include1,1-bis(1,1-dimethylethylperoxy)cyclohexane,1,1-bis(1,1-dimethylbutylperoxy)cyclohexane,4,4-bis[(t-butyl)peroxy]butyl pentanoate, dicumyl peroxide, t-butylα-cumyl peroxide, 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane,2,5-bis(t-butylperoxy)-2,5-dimethyl-3-hexin, dibenzoyl peroxide,bis(4-methylbenzoyl) peroxide, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, t-butyl peroxybenzoate, and t-hexylperoxybenzoate.

In the case where the styrene polymer is crosslinked using thecrosslinking agent, the amount of the crosslinking agent to be used canbe generally 1 part by mass or more and 10 parts by mass or less withrespect to 100 parts by mass of the styrene polymer.

For obtaining the crosslinked elastomer by crosslinking the styrenepolymer, a crosslinking aid may be used in combination with theaforementioned crosslinking agent. The crosslinking aid preferably hasat least one of an acryloyl group and a methacryloyl group, preferably aplurality of them. Among these, a compound represented by formula (1)below is suitable as a crosslinking aid used in combination with thecrosslinking agent for crosslinking the styrene polymer:X¹-A¹-R¹-A²-X²  (1)

where “R¹” represents an alkylene having a chain length of 2 to 10carbon atoms or a substituted alkylene in which a hydrogen atom of thealkylene is substituted with a substituent, “A¹” and “A²” eachindependently represent a direct bond or an ether bond, and “X¹” and“X²” each independently represent an acryloyl group or a methacryloylgroup.

In formula (1) above, “R¹” preferably has a structure represented byformula (2) below:

where “R²” and “R³” represent a hydrogen atom, a hydroxyl group, analkyl group having 2 to 3 carbon atoms, a (meth)acryloyloxy group, a(meth)acryloyloxymethyl group, or a (meth)acryloyloxyethyl group.

In the compound represented by formula (1) above, it is preferable thatboth “A¹” and “A²” be ether bonds, either “X” or “X²” be an acryloylgroup, and the other be a methacryloyl group. Further, in formula (2)above, it is particularly preferable that either “R²” or “R³” be ahydrogen atom, and the other be a hydroxyl group.

That is, it is particularly preferable that the crosslinking aid be2-hydroxy-3-acryloyloxypropyl methacrylate represented by formula (3)below:

Further, in the compound represented by formula (1) above, it ispreferable that both “A¹” and “A²” be ether bonds, and both “X¹” and“X²” be methacryloyl groups, and in formula (2), it is preferable thateither “R²” or “R³” above be an ethyl group, and the other be amethacryloyloxy methyl group. That is, preferable examples of thecrosslinking aid also can include trimethylolpropanetrimethacrylaterepresented by formula (4) below:

Use of such a preferable crosslinking aid as mentioned above allows thethermoplastic elastomer to exert excellent abrasion resistance, so thatthe thermoplastic elastomer can be a material suitable for theshoe-forming member. In the case of using the crosslinking aid togetherwith the crosslinking agent for crosslinking the styrene polymer, thehigher the amount of the crosslinking aid used, the more the abrasionresistance is improved. Accordingly, in general, the content of thecrosslinking aid is preferably 1 part by mass or more, more preferably 5parts by mass or more, particularly preferably 10 parts by mass or more,with respect to 100 parts by mass of the styrene polymer. Morespecifically, when crosslinking the styrene polymer, the content of thecrosslinking aid is preferably 0.03 mol or more, more preferably 0.05mol or more, with respect to 100 parts by mass of the styrene polymer.The crosslinking aid does not need to be contained in an excessiveamount, and the upper limit thereof is generally about 100 parts by masswith respect to 100 parts by mass of the styrene polymer, and is about 1mol with respect to 100 parts by mass of the styrene polymer.

The thermoplastic elastomer may further contain additives other thanabove, and examples of the additives include a hardness modifier such asparaffin oil, a tackifier such as terpene resin, an anti-aging agent, aprocessing aid, an inorganic filler, a silane coupling agent, anantibacterial agent, a perfume, and a pigment.

Among these, paraffin oil is a component effective for adjusting thetexture of the thermoplastic elastomer corresponding to the purpose. Inthe case where the thermoplastic elastomer contains paraffin oil, theratio of the paraffin oil is preferably 10 parts by mass or more and 50parts by mass or less, with respect to 100 parts by mass of the total ofthe polypropylene resin, the aromatic polymer, and the crosslinkedelastomer.

Since the fluidity of the polypropylene resin and the aromatic polymerconstituting the matrix is exerted by heating, the thermoplasticelastomer can be easily shaped to a desired shape by various moldingmethods such as injection molding, transfer molding, and press molding.That is, the thermoplastic elastomer is suitable as a forming materialfor forming the reinforcing sheet material 21 and the outer sole 4 usingsuch a molding method as mentioned above. Moreover, the thermoplasticelastomer has excellent adhesiveness. Accordingly, in the case where thereinforcing sheet material 21 is formed using the thermoplasticelastomer, the need to employ a special bonding method, for example, forforming the upper material 2 by bonding the reinforcing sheet material21 to another sheet can be eliminated. Further, in the case where theouter sole 4 is formed using the thermoplastic elastomer, the need toemploy a special bonding method, for example, for bonding the outer sole4 to the midsole 3 can be eliminated.

As described above, a shoe-forming member using the thermoplasticelastomer of this embodiment has not only excellent recyclability butalso an effect of facilitating the production of shoes. The shoe-formingmember of the present invention may be formed using only thethermoplastic elastomer as mentioned above or may be formed using othermaterials such as fabrics and non-woven fabrics in combination. Further,the shoe-forming member of the present invention may be formed byfoaming the aforementioned thermoplastic elastomer using a foaming agentor the like.

The thermoplastic elastomer of this embodiment also has excellentabrasion resistance. Accordingly, in the case where the thermoplasticelastomer is contained only partially in the shoe-forming member, thethermoplastic elastomer is preferably contained in exposed portions onthe outer surface and the inner surface of the shoe for allowing theshoe-forming member to exert the effect on the abrasion resistance.Further, conventionally known technical matter relating to shoe-formingmembers can be employed also for the shoe-forming member of the presentinvention, as long as the effects of the present invention are notsignificantly impaired.

EXAMPLES

Next, the present invention will be described further in detail by wayof examples. However, the present invention is not limited to theseexamples.

Evaluation 1: Abrasion Resistance and Peel Strength

(Production of Thermoplastic Elastomer)

The following materials (a) to (e) were supplied to a twin screwextruder so as to be kneaded in the twin screw extruder, so that thekneaded mixture was dynamically crosslinked, and a dry blended mixtureof the kneaded mixture and material (f) was supplied to an injectionmolding machine, to produce a test piece in the injection moldingmachine.

-   -   (a) Styrene polymer (SEEPS): 100 parts by mass    -   (b) Paraffin oil (P-200): 100 parts by mass    -   (c) Crosslinking agent (organic peroxide        (2,5-dimethyl-2,5-bis(t-butylperoxy)hexane)): 2 parts by mass    -   (d) Crosslinking aid (2-hydroxy-3-acryloyloxypropyl        methacrylate): 10 parts by mass    -   (e) Polypropylene resin (homo-PP): 20 parts by mass    -   (f) Poly-α-methylstyrene resin: 30 to 380 parts by mass        (Evaluation Method)

The thus obtained test piece made of thermoplastic elastomer wasevaluated based on the following criteria.

-   -   1) Hardness: JIS K6301:1975 Spring hardness tester, Type A,        Instantaneous    -   2) Density: JIS K7112:1999 Method for measuring density and        specific gravity of plastic-non-foamed plastic, Underwater        displacement (23° C.)    -   3) Tensile strength: JIS K6301:1975 Dumbbell No. 2, “Tensile        strength at break”    -   4) Elongation: JIS K6301: 1975 Dumbbell No. 2, “Elongation at        break”    -   5) Tear strength: JIS K6301: 1975 Type B    -   6) DIN abrasion: JIS K6264-2: 2005 (Method B, Temperature: 23°        C., Applied force to test piece: 10 N, Wear distance: 40 in)    -   7) Peel strength (adhesiveness): JIS K 6854-2 (T-type peeling        method, Rigid adherend: Test piece made of thermoplastic        elastomer (coated with primer), Adherend: Urethane flat plate;        rigid adherend and adherend were adhered together using urethane        adhesive, Test temperature: 20±3° C., Distance between chucks:        20 mm, Tensile speed: 0.00083±0.00004 m/s).

A primer generally used for olefin materials (such as a primercontaining chlorinated polypropylene) was used.

These evaluation results on the content of poly-α-methylstyrene resin inthe thermoplastic elastomer were summarized as follows.

TABLE 1 Content Tensile Tear DIN Peel (parts by mass) Hardness Densitystrength Elongation strength abrasion strength (a) to (e) (f) JIS-Ag/cm³ MPa % kgf/cm mm³ kgf/2 cm No.1-1 (a): 100  30 51 0.90 8.0 101129.9 143.9 2.5 No.1-2 (b): 100  80 53 0.90 7.9 878 34.8 115.0 4.1 No.1-3(c): 2 130 55 0.91 9.9 820 36.4 111.4 4.5 No.1-4 (d): 10 180 57 0.9112.5 769 42.2 87.6 5.5 No.1-5 (e): 20 280 60 0.91 17.3 708 39.9 98.6 6.9No.1-6 380 62 0.91 19.9 673 38.8 106.3 7.2

It is understood from the above results that the thermoplastic elastomerhas excellent adhesiveness and excellent abrasion resistance bycontaining 150 parts by mass or more of poly-α-methylstyrene resin (f)(7.5 times or more with respect to polypropylene resin (e)).

<Evaluation 2: Abrasion Resistance and Peel Strength>

Using the following three types (a1) to (a3) of styrene polymer (a) andthe following five types (d1) to (d5) of crosslinking aid (d), relativecomparison of abrasion resistance was conducted.

-   -   a) Styrene polymer        -   (a1) SEEPS        -   (a2) SEBS        -   (a3) SBS    -   d) Crosslinking aid        -   (d1) 2-hydroxy-3-acryloyloxypropyl methacrylate        -   (d2) Trimethylolpropanetrimethacrylate        -   (d3) Ethylene glycol dimethacrylate        -   (d4) Triallyl isocyanurate (TAIC)        -   (d5) Polyethylene glycol (#600) diacrylate            (Evaluation Method)

A test piece was produced in the same manner as in “Evaluation 1” aboveexcept that the content of crosslinking aid (d) in the raw materials forforming the thermoplastic elastomer was adjusted to 0.1 mol/kg or 0.06,and the content of poly-α-methylstyrene resin (f) with respect to 100parts by mass of the styrene polymer (a) was adjusted to 280 parts bymass, and an evaluation was conducted in the same manner as in“Evaluation 1”. The evaluation results are shown below.

TABLE 2 Content Tensile Tear DIN Peel (parts by mass) Hardness Densitystrength Elongation strength abrasion strength (a) to (e) (c) (d) JIS-Ag/cm³ MPa % kgf/cm mm³ kgf/2 cm No.2-0 0 0 — 0.90 — — — 132.1 — No.2-1(a1): 100 2 (d1): 10 60 0.91 17.3 708 39.9 98.6 6.9 No.2-2 (b): 100 2(d2): 20 60 0.91 16.0 752 39.3 94.5 5.2 No.2-3 (e): 20 2 (d3): 10 580.91 14.6 762 40.4 109.5 6.0 No.2-4 (f): 280 2 (d4): 25 — 0.92 — — —135.1 — No.2-5 2 (d5): 40 — 0.92 — — — 138.3 — *The content of materials(d1) to (d5) in the total compounding agents was adjusted in 0.1 mol/kg.

TABLE 3 Content (parts by mass) Density DIN abrasion (a) to (e) (c) (d)g/cm³ mm³ No. 3-0 (a2): 100 0 0 0.91 126.8 No. 3-1  (b): 100 2 (d1): 6 0.91 123.3 No. 3-2 (e): 20 2 (d2): 10 0.91 117.0 No. 3-3   (f): 280 2(d4): 12 0.92 145.7 * The content of materials (d1), (d2) and (d4) inthe total compounding agents was adjusted to 0.06 mol/kg.

TABLE 4 Content (parts by mass) Density DIN abrasion (a) to (e) (c) (d)g/cm³ mm³ No. 4-0 (a3): 100 0 0 0.92 125.6 No. 4-1  (b): 100 2 (d1): 6 0.92 157.8 No. 4-2 (e): 20 2 (d2): 10 0.92 172.3 No. 4-3   (f): 280 2(d4): 12 0.93 232.6 * The content of materials (d1), (d2) and (d4) inthe total compounding agents was adjusted to 0.06 mol/kg.

From the above results, it can be seen that a crosslinked elastomerobtained by crosslinking SEEPS (a1) is particularly preferable in thetypes of styrene polymer as the domain of the thermoplastic elastomer.Further, the aforementioned evaluation results show that even apolyolefin thermoplastic elastomer exerts excellent adhesiveness andexcellent abrasion resistance by containing an aromatic polymer having apoly-α-methylstyrene structure in its matrix.

<Evaluation 3 (Reference Evaluation): Content of Crosslinking Aid>

(Evaluation Method)

A test piece without containing poly-α-methylstyrene resin (f) wasproduced by changing the content of polypropylene resin (e) in the rawmaterials for forming the thermoplastic elastomer from 20 parts by massto 60 parts by mass, and an evaluation was conducted in the same manneras in “Evaluation 1”. The evaluation results are shown below.

TABLE 5 Content Tensile Tear DIN (parts by mass) Hardness Densitystrength Elongation strength abrasion (a) to (e) (d1) JIS-A g/cm³ MPa %kgf/cm mm³ No.5-0 (a1): 100  0 (0) 70 0.89 10.5 993 31.3 119.7 No.5-1(b): 100  1 (0.005) 70 0.89 9.7 851 33.7 117.7 No.5-2 (c): 2  5 (0.023)70 0.89 8.4 862 32.6 108.5 No.5-3 (e): 60 10 (0.047) 70 0.90 11.0 86634.3 97.7 No.5-4 (f): — 30 (0.140) 72 0.92 12.3 863 39.4 80.5 *Theparentheses in the content of (d) represent the number of moles withrespect to 100 parts by mass of the styrene polymer.

From the aforementioned results, it can be seen that a higher amount ofthe crosslinking aid to be used is advantageous for obtaining athermoplastic elastomer having excellent abrasion resistance.

Also from the above evaluation results, it can be understood that thethermoplastic elastomer according to this embodiment is suitable as amaterial of a shoe-forming member.

REFERENCE SIGNS LIST

-   -   1: Shoe    -   2: Upper material    -   3: Midsole    -   4: Outer sole    -   21: Reinforcing sheet material

The invention claimed is:
 1. A shoe-forming member comprising athermoplastic elastomer, the thermoplastic elastomer comprising: amatrix comprising a polypropylene resin and a poly-α-methylstyreneresin; and a domain comprising a crosslinked elastomer, wherein acontent of the poly-α-methylstyrene resin is 1.5 times or more of thatof the polypropylene resin.
 2. The shoe-forming member according toclaim 1, wherein the domain comprising the crosslinked elastomer iscovered by the polypropylene resin.
 3. The shoe-forming member accordingto claim 1, wherein the content of the poly-α-methylstyrene resin is 7.5times or more of that of the polypropylene resin.
 4. The shoe-formingmember according to claim 1, wherein the crosslinked elastomer is formedby crosslinking of a styrene polymer using a crosslinking agent and acrosslinking aid, and the crosslinking aid is a compound represented byformula (1) below:X¹-A¹-R¹-A²-X²  (1) where R¹ represents an alkylene having a chainlength of 2 to 10 carbon atoms or a substituted alkylene represented byformula (2) below in which a hydrogen atom of the alkylene issubstituted with a substituent, A¹ and A² each independently represent adirect bond or an ether bond, and X¹ and X² each independently representan acryloyl group or a methacryloyl group:

where R² and R³ represent a hydrogen atom, a hydroxyl group, an alkylgroup having 2 to 3 carbon atoms, a (meth)acryloyloxy group, a(meth)acryloyloxymethyl group, or a (meth)acryloyloxyethyl group.
 5. Theshoe-forming member according to claim 1, wherein the crosslinkedelastomer is formed by crosslinking styrene-ethylene-butylene-styrenecopolymer resin (SEBS) or styrene-ethylene-ethylene/propylene-styrenecopolymer resin (SEEPS).
 6. A shoe comprising the shoe-forming memberaccording to claim 1.